1. Field of the Invention
The invention relates to electrical connectors of the type which have contacting devices for establishing an electrical contact with contacting devices of external terminals.
Such electrical connectors, usable for connecting printed circuit boards but also for connecting individual cables or cable harnesses, are known in a great number of forms.
2. Description of the Related Art
As a representative, reference may be made in this connection for instance to the 2.5 mm family of plug connectors known as SIPAC, made and sold by Siemens. Descriptions of the basic model and of further developments of this electrical connector have been published in "Components", 30 (1992), No. 5, pp. 189-192 and in "Markt und Technik--Wochenzeitung fur Elektronik" [Market and Technology--Electronics Weekly] No. 26, Jun. 24, 1994, pp. 36-37.
As may be learned from the above publications, major effort has been devoted recently to making the known electrical connectors HF-compatible.
The need for HF-compatible electrical connectors is steadily increasing. This is because on the one hand the signals to be transmitted via the electrical connectors are increasingly digital signals, whose error-free transmission, because of the steep signal edges they contain, requires a frequency band extending into the HF range even at low transmission rates. On the other hand, the transmission rates demanded are increasing steadily as well and have meanwhile already reached orders of magnitude of GBit/s.
For the reasons given above, the electrical connectors must have reflection, impedance and crosstalk properties that enable distortion and interference-free transmission at even the highest frequencies.
Various attempts have already been made in the past to this end.
For instance, to reduce crosstalk, it is possible for channels to be transmitted to be carried over only every other contact, while the intervening contacts are connected to common ground. However, in such an embodiment, the number of terminals usable for signal transmission is drastically reduced, so that it appears relatively useless for applications with high signal density.
It has become known heretofore from German Patent DE 40 40 551 C2 to prevent crosstalk between adjacent terminals in adjacent vertical rows by inserting a shielding element between the vertical connection rows of a female multipoint connector. A disadvantage of this embodiment, however, is that of the five available rows of contacts, only three rows are usable for signals, since two rows are occupied by ground.
On the other hand, European patent publication EP 0 486 298 A1 discloses a connector configuration in which ground contacts are disposed between signal contacts, each offset by one-half the pitch, so that the signal contacts in the mounted state are surrounded by ground contacts. That configuration is less than ideal in the sense that the individual contacts which connect to ground must all be contacted individually to the printed circuit boards, which makes it considerably more difficult to untangle the signal lines.
From the periodical already mentioned above, "Markt und Technik--Wochenzeitung fur Elektronik" [Market and Technology--Electronics Weekly] No. 26, Jun. 24, 1994, pp. 36-37, it has become known heretofore to provide continuous shielding of each individual contact with a tight sonuare metal shaft. The "lattice" of lengthwise and crosswise metal plates required for this shaft, which are spaced apart 2.5 mm in the exemplary embodiment described, is disposed entirely inside the female multipoint connector. At the penetration points of the crosswise and lengthwise plates, closely spaced slits must therefore be provided, which mesh with one another and which make high-grade electrical contact with one another; this clearly requires considerable engineering effort and entails high additional costs.
The above-described prior art options for reducing distortion and/or interference in signal transmission have the disadvantage that either a great number of additional ground contacts or complicated shielding of the individual contacts must be provided. This entails considerable added expense in manufacture and/or in the use of the connectors. Aside from this, even in the ways described above, the distortion and/or interference occurring in signal transmission cannot be elimianated entirely, so that the efforts made thus far have not been satisfactory, either financially or technologically.